Getting variable size in C preprocessor

Question

i have an problem, i am writing a header file, which depending on the Sizes of the c standard datatypes, defines different Structs and Unions. I would need something like this:

#if sizeof(int) == 4
    typedef struct {
        int i;
    } test;
#else
    typedef struct {
        long i;
    } test;
#endif

sadly this doesnt work.

Does somebody know, how i can do this?

Thanks for your help.

#if INT_MAX == 2147483647 ... remember to #include <limits.h> — pmg
– pmg, Commented May 13, 2020 at 16:18

0___________ · Accepted Answer · 2020-05-13 14:37:55Z

2

You cant do it this way as preprocessor does not know anything about the C language, but for this purpose you have fixed size integer types which are standard and portable

typedef struct {
    int32_t i;
} test;

answered May 13, 2020 at 14:37

0___________

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Comments

datenwolf · Accepted Answer · 2020-05-13 14:29:55Z

0

Strictly speaking, you can't. What you can do however is take "well known" preprocessor definitions as hints to decide which architecture, compiler and OS you're targeting and decide from that.

answered May 13, 2020 at 14:29

datenwolf

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